The development and acceptance of wind energy as a clean and productive source of alternative energy is proliferating. Wind energy can be captured by a wind turbine generator, which is a rotating machine that converts the kinetic energy of the wind into mechanical energy, and the mechanical energy subsequently into electrical power. Common horizontal-axis wind turbines include a tower, a nacelle located at the apex of the tower, and a rotor that is supported in the nacelle by means of a shaft. The shaft couples the rotor either directly or indirectly with a rotor assembly of a generator housed inside the nacelle. A plurality of wind turbine generators may be arranged together to form a wind park or wind power plant.
The significant growth in acceptance of wind power generation has led to various countries and electrical grid operators implementing stringent grid connection requirements, also known as grid codes. Some grid codes require a wind power plant to meet a certain reactive power requirement such that the wind power plant is capable of importing and/or exporting reactive power during voltage disturbances in the grid.
Power factor can be generally be defined as the ratio of real power flowing to the load to the apparent power in the circuit. Generally, the grid requirements are defined in terms of absolute power factor values, which depend on active power dispatched by the wind power plant, at the point of common coupling.
Some grid codes, however, do define their power factor requirement as an amount of reactive power imported or exported based on the nominal rating of the WPP and irrespective of the active power generation. As such, power factor requirement can be identified as a reactive power requirement. In such cases, additional reactive power compensation is required for the wind power plant to meet the grid code. Typically, this compensation is provided by a dynamic reactive power source, such as a static synchronous compensator (STATCOM) or a static VAR compensator (SVR). However, such compensation equipment can be prohibitively expensive, for example, US$1 M for a 5 MVAR STATCOM, which adversely increases the capital costs for implementing a wind power plant.
Further, complications may arise, if for some reason, the reactive power compensation for which the wind power plant relies on for grid code compliance becomes unavailable. As a result, the wind power plant would not be able to meet grid code requirements at full generation, which may lead to financial penalties for the plant operator.